Infestation of rodents, particularly rats and mice, in places people live and work has been a persistent problem for mankind. To eliminate rats and mice, traps of various kinds are frequently used. However, traps can be hazardous to small children and pets. Furthermore, traps are distasteful to many persons and because they require regular checking and removal of killed rodents.
Poisons of various kinds are also frequently used to eliminate rodents. The rodents ingest the poisons and are killed. Poisons, however, are undesirable because they pose a safety hazard to humans, especially children, and small pets. Poisons also are environmentally undesirable since they may ultimately enter ground water or streams. Over time, rodents may also become immune to certain poisons.
In any event, use of poisons does not eliminate the distasteful task of removal of the dead rodents. Furthermore, where poisons are used in enclosed interior spaces such as buildings, the rodents will frequently go into inaccessible areas behind walls after they ingest the poison. After the rodents die, a putrid odor may exist and become so severe as to require demolition of the wall to remove the dead rodent.
In any event, many persons find it distasteful to kill rodents and would prefer to simply repel rodents from an area. To this end, ultrasonic electronic devices have been tried. However, these devices have limited effectiveness, require a nearby electrical outlet, and may irritate house pets.